update rich text toolbar comment button to reflect state

www/pad/comment.js

@@ -68,7 +68,7 @@
             };
 
             // Register the command.
-            editor.addCommand('comment', {
+            var command = editor.plugins.comments.command = editor.addCommand('comment', {
                 exec: function(editor) {
                     if (editor.readOnly) { return; }
                     editor.focus();

www/pad/comments.js

@@ -812,9 +812,13 @@ define([
         });
         $(Env.ifrWindow.document).on('selectionchange', function() {
             removeCommentBubble(Env);
-            var applicable = Env.editor.plugins.comments.isApplicable();
-            if (!applicable || !isEditable(Env.ifrWindow.document)) { return; }
+            var comments = Env.editor.plugins.comments;
+            var applicable = comments.isApplicable();
+            if (!applicable || !isEditable(Env.ifrWindow.document)) {
+                return void comments.command.setState(0);
+            }
             addCommentBubble(Env);
+            comments.command.setState(2);
         });
     };